This invention relates to a gas generator for producing high pressure gas by burning expansible combustible material, and more particularly to a pulse type, multi-chamber gas generator which provides a flow of output gas for operating a turbine and the like by internally combusting fuel and air in at least one of the chambers.
Apparatus constructed according to the present invention has a pair of interconnected chambers, at least one of which comprises a combustion chamber utilized to burn at least a portion of the fuel introduced thereto. As the fuel is burned expanding gases are produced in the combustion chamber. A portion of the expanded gases is utilized to provide a useful power work output and another portion of the expanded gases is blown through a passage to a second chamber and forces unburned fuel in the combustion chamber into the second chamber. The pressure in the combustion chamber will lower so that the gas and unburned fuel in the second chamber will be redrawn into the combustion chamber. As the gas and unburned fuel pass between the chambers in the passage, additional fuel will be drawn into the chambers.
An object of the present invention is to provide a multi-chamber gas generator of the type described including a chamber-connecting passage having a throat of reduced cross section which is used as a venturi system to suck fuel into at least one of the chambers and pass gas and unburned fuel between the chambers.
When fuel is ignited in the combustion chamber, burning normally expands radially outwardly in all directions to produce an outwardly expanding fire ball. The high temperature, expanding gases of combustion, create an expanding high-pressure sphere which precedes the outwardly expanding flame front. The speed of expansion of the high-pressure sphere exceeds the speed of the flame front. This forces a substantial portion of unburned fuel to be expelled from the combustion chamber into the passage connecting the chambers before it has been consumed by the flame. When the unburned fuel is passed from the combustion chamber through the passage into the other chamber, the gas and fuel expelled into the passage must be cooled to prevent preignition of any fuel being sucked into the passage. Accordingly, it is an object of the present invention to provide a gas generator of the type described having a heat exchanger which cools the fuel being expelled from the combustion chamber below the flash point of the fuel.
The nature of the expanding flame front and the expanding gases makes the location of the outlet port and the igniter important. If the igniter were in the center of the chamber, unburned fuel would tend to be expelled through the outlet.
Another object of the present invention is to provide a multi-chamber gas generator of the type described including a combustion chamber, and an exhaust port in the combustion chamber positioned substantially diametrically opposite the passage which connects the chambers.
A further object of the present invention is to provide apparatus of the type described including heat exchanger mechanism in the passage for cooling expelled fuel below the flash point.